1. Field of the Invention
This invention relates to a multi-piece solid golf ball comprising a solid core, an intermediate layer and a cover. More particularly it relates to a multi-piece solid golf ball in which the overall hardness distribution of the ball is optimized to provide satisfactory all-round performance including flight performance, durability, feel, and control.
2. Prior Art
Golf balls having a variety of constructions are available on the market. Of these, the majority of golf balls now on the market are two-piece solid golf balls having a rubber-based core enclosed within a cover made of ionomer resin or the like, and thread-wound golf balls comprising a solid or liquid center about which is wound a rubber thread which is in turn enclosed within a cover.
Most golfers of ordinary skill use two-piece solid golf balls because of their excellent flight performance and durability. However, the two-piece solid golf balls have a very hard feel when hit, and are difficult to control because of the rapid separation of the ball from the head of the club. For this reason and others, many professional golfers and low-handicap golfers prefer thread-wound golf balls to two-piece solid golf balls. Although thread-wound golf balls have a superior feel and controllability, their flight distance and durability fall short of those for two-piece solid golf balls.
Since two-piece solid golf balls and thread-wound golf balls provide mutually opposing features, golfers select which type of ball to use based on their level of skill and personal preference.
This situation has prompted efforts to approximate the feel of a thread-wound golf ball in a solid golf ball. As a result, a number of soft, two-piece solid golf balls have been proposed. A soft core is used to obtain such soft two-piece solid golf balls, but making the core softer lowers the resilience of the golf ball, compromises flight performance, and also markedly reduces durability. As a result, not only do these balls lack the excellent flight performance and durability characteristic of ordinary two-piece solid golf balls, but they are often in fact unfit for actual use. More specifically, the structure of prior art two-piece solid golf balls is determined depending on which of the four features of softness, resilience, spin and durability is of more importance. Any attempt to improve one of these features compromises the remaining features.
As a matter of course, controllability is also necessary upon full shots with a wood, typically a driver or a long iron. If a soft cover is used in a ball because too much attention is paid to the purpose of improving the spin properties upon control shots or approach shots with a short iron, the ball would receive a too great a spin rate upon a shot with a driver (which causes greater deformation) and sky or rise too high, resulting in a reduced carry. By contrast, if the ball receives a too small a spin rate, the ball will prematurely drop in its fall trajectory, which is also detrimental to the ultimate carry. This means that an appropriate spin rate is necessary upon driver shots too.